Field of Invention
The present invention belongs to the fields of photoelectron and optical communication, and relates to an ultrahigh-resolution photonic-crystal superprism and a method for designing the same.
Description of Related Arts
A photonic crystal was independently proposed by S. John and E. Yablonovitch in 1987, respectively, it is an artificial microstructure formed by mediums which have different refractive indexes with periodically arranging. Because a dielectric constant has periodicity in space, a spatial refractive index is periodically changed. When the change of the dielectric constant is large enough and the period of the change is equal to the wavelength of light, the dispersion relation of light wave will have a band structure, that is, Photonic Band structures. These terminated frequency intervals are called as “Photonic Band Gap” (PBG), light or electromagnetic wave whose frequency falls within a forbidden band may not be propagated. A periodic dielectric structure with the “Photonic Band Gap” is called as the photonic crystal.
The refractive index of the photonic crystal changes periodically in space, which may effectively control the propagation of photons. Since the concept of the photonic crystal has been put forward, people give extensive attention to the application of the photonic crystal. Especially in the field of optical communication technology, a photonic crystal fiber, a micro resonator laser, a filter, an integrated optical path and other photonic crystal devices have broad application prospects. The continuous improvement in the microfabrication technology of a semiconductor material has greatly promoted the application of a 2-dimensional or even 3-dimensional photonic crystal device in practice. In recent years, a photonic-crystal superprism and its design for a high-performance spectrometer and a wavelength division multiplexer have become the focus of attention in the industry, because the spectrometer and the wavelength division multiplexer are one of core devices in the optical communication, optical detection and other fields.
The photonic-crystal superprism has the ability to separate the electromagnetic wave with a continuous frequency within the photonic crystal in accordance with a certain number of channels. It is characterized by the followings: on one hand, this wavelength division multiplexer has small volume and is easy to be integrated; on the other hand, it has a very high frequency (wavelength) resolution. The existing literatures have disclosed a photonic-crystal superprism, it uses an area where a constant-frequency contour of the photonic crystal has a sharp change to work. This kind of the superprism inevitably has frequency missing, easy crosstalk, a relatively large device area and other problems, therefore, it is not conducive to the application of the device in the integrated optical path.
Therefore, in order to avoid the above problems, we have to take a new physical mechanism to get a new type of photonic crystal superprism through a new design.